Orthopedic surgeon, Dr. Lisa Niles, arrived in Port Charles in November 2009 seeking a patient consult from Dr. Robin Scorpio-Drake. Lisa turned out to be the former medical school classmate and girlfriend of Robin's husband, Dr. Patrick Drake. Assuring Robin that she had no lingering feelings for Patrick, the trio became friends, and Lisa was soon hired at General Hospital.
Lisa, Patrick, and the new Chief of Staff, Steve Webber spent many nights sharing drinks at Jake's. Robin often chose to go home to her daughter, which began to cause friction in the Scorpio-Drake marriage. At Jake's, Lisa and Patrick would flirtatiously remember their wild college days, when Patrick was a free-spirit and lady's man. Lisa could not accept or understand the fact that Patrick chose to settle down and start a family.
Lisa noticed that Patrick seemed to get jealous whenever she showed an interest in Steve, so Lisa began to pursue Steve in earnest. Steve and Lisa slept together, but Steve quickly realized that Lisa was more interested in Patrick than in him. Steve was a bit hurt, so he broke things off with Lisa, but remained friends with her. Meanwhile, the Scorpio-Drake marriage was floundering. It didn't help when Robin decided to go to Africa to work on a project to honor her log-lost love, Stone.
Patrick felt abandoned and confused, so he spent more time with Lisa under the guise of friendship. One evening, after completing a successful surgery together, Lisa and Patrick got drunk and had a one-night stand. Patrick immediately regretted breaking his marriage vows. Lisa quickly assured Patrick that it hadn't been a big deal and that she wouldn't breathe a word of their one-night stand to anyone. However, upon Robin's return from Africa, Lisa took every opportunity to drop hints.
Lisa then began to throw herself at Patrick who repeatedly rebuffed her advances. She became increasingly unstable and began to lash out at Robin through a series of increasingly disturbing methods.
Lisa broke into Patrick and Robin's home, cut Robin's face out of her wedding photo, and then stole Robin's HIV meds. She also secretly defaced pictures of Robin, which she then planted in Robin's work locker. Things reached a crisis point when Lisa briefly kidnapped Emma and then innocently claimed that she had merely taken Emma for ice cream. This incident prompted Patrick to reveal his affair to Robin, which lead to Robin and Patrick's separation.
Robin threatened Lisa with consequences if Lisa went near her family again. Lisa made the most of the situation and tried to comfort Patrick during his separation from Robin. At the same time, she continued to terrorize Robin while trying to make Robin seem like she was the mentally unstable one. Lisa threw herself in front of Robin's moving car and told the police that Robin had hit her intentionally. Lisa also trashed her own locker by splattering it with blood and then accused Robin of the crime.
Lisa's crime spree and jealousy escalated when she secretly boiled Emma's stuffed rabbit in Robin's Bunsen burner. She then broke into Mac's house, where Robin was staying, and replaced Robin's HIV meds with strong sedatives. After Robin crashed, she found herself in a cabin with Lisa. Lisa insisted that it had been a coincidence that Robin had stumbled into the cabin that one of Lisa's patients had loaned out to Lisa. Robin didn't believe Lisa, so she fled the cabin. Unfortunately for Robin, she stumbled into a dry well.
Satisfied that Robin was out of the way, Lisa returned to Port Charles. Lisa kept quiet even though Patrick and others were frantically searching for Robin. Patrick suspected that Lisa was behind Robin's disappearance, so he and Steve figured out where Lisa might have stashed Robin. Patrick showed up to rescue Robin in the nick of time.
Lisa was just minutes behind Patrick. Lisa pointed a gun at the couple and then declared her love for Patrick. Lisa then turned the gun on herself and threatened suicide. Patrick talked her down until Mac showed up and arrested Lisa.
Instead of going to jail, Lisa went to Shadybrook for a very brief stay. Once released, she returned to work at General Hospital and continued to make Robin appear to be unstable and jealous. On Halloween, Lisa briefly kidnapped Emma for a second time, but left Emma near Kelly's to make it appear that Robin was paranoid and unfit.
On Emma's birthday, Lisa showed up in time to find Mac's house in flames. She raced inside and saved Robin and Emma. Robin accused Lisa of setting the fire, so Lisa was taken to the police station for questioning. At the police station, Lisa denied that she had anything to do with the fire. According to Lisa, Robin was the unstable one and had falsely accused Lisa out of spite because of the affair. Lisa was cleared of any charges related to the fire when the arson report was inconclusive but mentioned a candle had been lit near a curtain.
Lisa continued to push Robin to act erratically. While Robin recuperated in the hospital, Lisa stood over her with a syringe and threatened her. When Robin called for help, Lisa claimed she was only checking on Robin and said the syringe was for the patient next door. Steve analyzed the syringe which backed Lisa's story. Lisa responded by explaining she was tired of Robin's accusations and decided to approach the hospital board to have Robin fired.
Lisa found Patrick at Jake's and offered to drop her pursuit to have Robin fired if Patrick would sleep with her again. Patrick was immediately offended by the idea and she quickly claimed she was joking and left. Lisa was concerned the board would not side with her when she saw Nikolas Cassadine, the head of the board, and Robin together. Robin hoped to use her personal friendship with Nikolas in her favor. Lisa happened upon Robin sleeping in her hospital room and started injecting a substance into her I.V. Maxie entered the room and caught Lisa in the act and Robin immediately ripped her I.V. out.
Lisa raced out of the room and quickly handed the syringe to Johnny Zacchara and asked him to get rid of the syringe. Johnny remembered Lisa as a juror that leaned in his favor when he was on trial for murder and he accepted the syringe. Without the syringe, Robin and Maxie had no proof Lisa had attempted to harm Robin and Lisa claimed it was another empty accusation made by Robin.
When Robin returned to work, Nikolas witnessed a few interactions between Lisa and Robin and he sided with Lisa. He explained to Robin there was no proof against Lisa and she was an outstanding doctor. He also warned Robin that she came off as the emotionally unstable person and needed to get control. Lisa started to feel vindicated and she found another support system via a blogging confessional site. She spoke about her affair with Patrick and the continual retribution she received from his wife and the online community expressed sympathy.
Although Lisa believed she had made a quick escape from the syringe incident, the ordeal was far from over. Johnny kept the syringe and used it to blackmail Lisa into providing him medical treatment in his home after he was shot. Lisa pretended she and Johnny were dating as a cover to explain her presence in his home. He refused to seek treatment in the hospital even when his wound was infected and continued to blackmail Lisa. He explained that in the event of his death, the syringe and how it came into his possession would be revealed. Lisa felt pressured to save Johnny and she stole medication from the hospital.
Robin and another eyewitness saw Lisa steal medication. When she was caught, she claimed she planned to give the medication to a relative of her housekeeper. The relative was unable to come to the hospital because of her illegal status in the country. Steve accepted the story and agreed Lisa could keep her job as long as she brought the patient in to the hospital. Lisa shared what had happened and Johnny provided a woman that was in the country illegally and in need of medical treatment.
Although Lisa had escaped any consequence for stealing medication from the hospital she was determined to end Johnny's blackmail. She gave Johnny a pill that knocked him out while she searched for the syringe. When he woke up, he admitted he knew she would try exactly what she had done and he again reminded her that if he died, her attempt on Robin's life would be revealed.
Instead of giving up her obsession, Lisa changed tactics. She encouraged a former lover and colleague named Terrell Jackson to take a pediatrics position at General Hospital. Terrell was interested in rekindling his affair with Lisa but she explained that Terrell would need to bed Robin first. Terrell agreed and he hid his past connection to Lisa. As Lisa had hoped, Robin was friendly with Terrell and they spent time together working on a project for the AIDS wing of the hospital.
While Terrell worked on wooing Robin, Johnny recovered and started visiting Lisa at the hospital. He claimed they were dating and forced Lisa to go along with the cover story, especially after Patrick remembered seeing Johnny in the corridor when Lisa supposedly had the syringe. Patrick correctly theorized aloud that Lisa must have passed the syringe to Johnny and he pressured Johnny to do the right thing and turn Lisa in.
Lisa felt the pressure of Patrick closing in on the truth and she responded by setting up Patrick to find Terrell and Robin in a compromising position. Lisa led Terrell to believe he was in store for a romantic evening with her but instead sent Robin to his room. Robin believed she was on her way to see Patrick, who arrived a few minutes later and was also sent to Terrell's room. Robin walked in on Terrell barely dressed and they laughed about the confusion. The mix-up was quickly sorted out but it caused Terrell to question the claims Robin made against Lisa and rethink his decision to break up the Scorpio marriage.
When the hotel room debacle backfired Lisa tried to drug Patrick's drink at Jake's. Johnny was also at Jake's and he arranged for Lisa to drink what she had intended for Patrick. She passed out and Johnny took her back to his place. When she recovered she wanted to know why Johnny had prevented her from drugging Patrick but then cared for her after she ingested the tainted drink. Johnny admitted he had a soft spot for Lisa because she reminded him of his sister Claudia and he told her Claudia's obsession with Sonny led to the choices that ended her life. Johnny encouraged Lisa to forget her obsession with Patrick and move on with someone else.
Johnny tried to be the "someone else" Lisa could move on with and they became lovers. Lisa was impressed and surprised when Johnny defended her in public and she told Johnny she was over Patrick. Although she continued to sleep with Johnny, she was actually working her next angle to get to Patrick. Lisa befriended Kristina Davis when she learned Kristina was baby-sitting Patrick and Robin's daughter. Lisa provided Kristina with herbal supplements to help her deal with the stress of waiting for college acceptance letters. The pills were actually narcotics.
Meanwhile Maxie Jones and Matt Hunter overhead a conversation between Lisa and Johnny in which Johnny admitted he had the syringe. Johnny knew his leverage over Lisa was about to end and he created a scavenger hunt for Lisa and Robin. Whichever woman found the syringe first would be in possession of it. Robin found the syringe first but when she was called away to deal with a hospital emergency Lisa took the syringe and destroyed it.
The influence of the narcotics on Kristina affected her judgment and she allowed Lisa into the Scorpio-Drake home as she baby-sat. Lisa used her time in Patrick and Robin's home to plant a wire and used it to eavesdrop. Listening to the conversations between the couple inspired Lisa and she researched gas leaks. Lisa also created a paper trail using Patrick's credit card number so it looked like he was engaging in an affair.
Once Lisa had everything in place she made her move to rid Robin from Patrick's life permanently. She sneaked into Robin and Patrick's home and created a gas leak. When Robin arrived home she made a noise to lure Robin to the basement and locked her inside. Lisa informed Robin she would be dead within the hour and Patrick would be blamed for her death. The tables were turned on Lisa when Patrick and Mac showed up to rescue Robin and Robin notified Lisa she recorded the entire conversation on her cell phone.
Lisa was taken to the police station and she turned to Johnny for help. Johnny was disgusted by Lisa's actions and refused to offer her assistance. Lisa was sent to Shadybrook and she remained there briefly until she escaped. Once she was free again she turned to Johnny. He agreed to help Lisa leave Port Charles. Johnny's father Anthony overheard the exchange and privately offered Lisa another option. He encouraged Lisa to remain in town and seek revenge against those who had wronged her and she agreed.
Lisa devised a final act of revenge assisted by Anthony. She disguised herself and sneaked into the hospital with a gun and a syringe. Lisa held Steve, Patrick, Robin, and Maxie hostage in the hospital conference room and held her own trial. She addressed each person and explained what they were guilty of. Maxie's ex-boyfriend Spinelli crawled through a heating vent and jumped in front of a bullet intended for Maxie. Lisa prevented any of the doctors in the room from attending to Spinelli.
Jason Morgan and Detective Dante Falconeri stormed into the room and broke up Lisa's trial. She managed to grab Robin and held the syringe to her neck. Patrick tried to reason with Lisa and saved Robin. In the scuffle, Lisa injected the syringe into herself. The syringe contained drain cleaner and she lapsed into a coma.
Anthony Zacchara visited Lisa several times while she was comatose and he revealed that he was her power of attorney. He ordered the doctors to pump Lisa full of medication until she woke up. His plan worked and Lisa emerged from her coma. Anthony wanted to use Lisa to seek revenge against Patrick since Patrick had foiled Anthony's attempt to murder Jason Morgan, but Lisa did not want any part of working with Anthony.
Lisa's refusal angered Anthony and he threatened to place her back in a coma if she did not follow his orders. Lisa escaped and learned that Patrick and Robin planned to attend a celebration for Matt Hunter. The party was going to take place on a chartered boat and Lisa decided to join the party. But first, Lisa decided to get rid of Anthony. She found him on the docks and stabbed him in the stomach. She pushed him in the water and left him to die.
After Anthony had been neutralized, Lisa paid Johnny a visit at his penthouse. He was shocked to see her and offered to help her get her life back on track. Lisa refused the offer and started to seduce him. While he was distracted, she used a syringe to inject him with a substance that caused temporarily paralysis. Johnny questioned why Lisa had turned on him and she explained that she had no interest in being saved and her focus was revenge on Patrick and Robin.
Although Johnny had begged Lisa to leave Patrick and Robin alone, Lisa secretly boarded the boat and watched the guests. She knocked out the first mate and disguised herself as a member of the crew. Anthony also arrived on the boat and offered to have an escape boat ready for Lisa after she exacted her revenge if she agreed to cooperate with Anthony. She declined the offer and told Anthony she had enough needles to deal with everyone on the boat on her own.
The captain of the boat found Lisa and recognized that she was an imposter. She silenced him with one of her needles and moved on with her plan. On her way, she ran into Elizabeth Webber and threw her off the boat after she knocked her out. Then Lisa chloroformed both Patrick and Robin and tied Patrick to a bed in one of the cabins. She tied Robin to a chair and came at her with a syringe. Lisa explained that since Patrick loved Robin so much, they should share everything, including Robin's HIV. She wanted to inject Robin's blood into Patrick.
Robin freed herself from the chair and went after Lisa. The women fought and Lisa pushed Robin into a set of stairs. By the time Robin recovered and the police arrived, Lisa was not on the boat. Two weeks later, Lisa's body washed up on shore and an autopsy revealed that she had died from blunt force trauma to the head. Her death was considered a homicide and the police opened an investigation into her death.